Yuiko's strength rivals Masato Inohara's as she is able to almost effortlessly blow a classroom door out of its mount the consequences of such action had put Masato to awe. Yuiko is Riki Naoe's classmate who is sometimes seen carrying a replica of a katana called Muramasa. Despite that, Yuiko regains her calm composure before she can actually commit a crime, which still doesn't cancel out the fact that she is truly fearsome when mad. It is shown in Kurugaya's route in the visual novel that she is very protective of her friends and if someone pisses her off, she gets insane and drops any doubt about killing a person if he or she is the cause of her madness. Yuiko is seen to be totally fearless which makes Riki wonder if there is anything that can discompose her. She is fond of things or people she considers to be cute, such as several of the female cast of characters, especially Rin Natsume and Komari Kamikita, though the way she expresses her fondness sometimes exceeds the edge of decency. Yuiko likes pulling pranks on Riki and joking indecently about him, his behavior, or his intentions. Though she mostly behaves like an adult, she never lets go of an opportunity to do something she considers to be funny. Riki Naoe sees her as a person that makes everyone around "conform to her pace". She is a very determined person, willing to break through any obstacles that are in her way. For that reason she is seen as an older sister to everyone despite being the same age of almost the entire cast, and is referred to as Anego ( Elder Sister) by Haruka Saigusa and herself. Yuiko is a self-sufficient, reliable and caring girl. Her uniform is the same as the other girls with the exception that she wears black stockings. Besides being the tallest of the girls, she also has the biggest breasts, for that reason, she doesn't completely close her shirt. Yuiko is the tallest girl of the entire group with long straight black hair that has a yellow ribbon on the left side of her hair and her eye color is something between blue and purple.